Effect of Sol-Gel Method for Medium Steel Phosphating Coating of Electrochemical Behavior

An attempt has been made to increase the corrosion resistance properties of medium steel substrate by using silica sol.The results show that: sol-gel method can increase corrosion resistance of phosphating coating. PS(silicon sol coated after phosphating )’s corrosion potential reduced more than P(phosphating sample)’s and its corrosion density also reduced.Polarizationg resistance of PS can improved many times.R2 of PS more reduced than P,but R3 improved more than ten times and R4 improved over sixty times by using equivalent circuit to fit EIS measurement. Corrosion resistance of PS was higher than that of P.